Operation Manual

Wireless Security White Paper 14
Core elements of a PKI are:
• Asymmetric keys
• Digital certificates
• Digital signatures
The following paragraphs describe and illustrate these elements.
A "key" is a numeric value of variable length that an encryption algorithm uses to convert
unencrypted text into encrypted text. Public key cryptography uses a pair of asymmetric keys for
encryption and decryption. An "asymmetric" key system uses a different key for encryption and
decryption. (By contrast, a "symmetric" key system uses the same key for encryption and
decryption.)
Each pair of keys in an asymmetric key system consists of a public key and a private key. The
public key is distributed widely. The private key is always kept secret. Data encrypted with the
public key can be decrypted only with the private key. Conversely, data encrypted with the
private key can be decrypted only with the public key. Most asymmetric encryption uses the RSA
algorithm developed in 1977 by Rivest, Shamir, and Adleman, or derivatives of that algorithm.
Figure 6 illustrates symmetric and asymmetric keys.
Figure 6: Symmetric and Asymmetric Keys
Symmetric Key vs Public Key
Symmetric key (shared secret) systems
Same key used for encryption and decryption
Symmetric key (shared secret) systems
Same key used for encryption and decryption
Public key systems
public key
private key
Different keys for encryption and decryption
Public key systems
public key
private key
Different keys for encryption and decryption